The present invention relates generally to semiconductor devices, and more specifically, to semiconductor devices that are protected from exposure to electromagnetic radiation.
The number and types of electronic systems in which semiconductor integrated circuits are being used continues to increase. New applications for integrated circuits often present new design and operating requirements. Most notably, the demand for the miniaturization of electronic systems forces the production of smaller and thinner integrated circuits (IC""s) that occupy a smaller xe2x80x9cfootprintxe2x80x9d on printed circuit boards. One way to reduce the footprint is to discard the package used to encapsulate the IC. Unpackaged IC""s contain bare silicon dies that have electrical contacts formed directly on a surface of the dies.
Unpackaged devices are preferably utilized in environments that are not exposed to certain energy levels of electromagnetic (EM) radiation. For instance, it is desirable to shield unpackaged devices from EM radiation having wavelengths greater than 700 nm (700xc3x9710xe2x88x929 m) because such radiation penetrates silicon. Such penetrating EM radiation adds energy into an IC, thereby possibly causing unwanted electron flow in the circuitry. This is referred to as xe2x80x9cdriftxe2x80x9d current. It is generally desired to protect unpackaged IC""s from infrared (IR) radiation, which has a wavelengths of approximately 700 nm-1 mm in length. It is usually sufficient to protect the devices from infrared radiation by placing the devices within enclosures which block out visible light. New electronic components, however, require unpackaged IC""s to operate in conditions which expose the IC""s to infrared radiation. For example, cellular phones, pagers, and personal digital assistants (PDA""s) contain infrared radiation sources such as sunlight, LEDs, or backlights. Unpackaged IC""s must be shielded from these IR sources in order to operate correctly in these environments.
Currently, a layer of epoxy is applied to unpackaged IC to block the transmission of IR radiation. A mark used for manufacturing purposes is then placed upon the layer of epoxy. The marking, (e.g., symbols, letters, etc.) is important because it allows the IC to be identified or it allows the IC""s orientation to be determined during a manufacturing process. Unfortunately, applying epoxy to the surface of unpackaged devices has certain disadvantages. First, the process of applying a layer of epoxy onto a semiconductor device requires a substantial amount of handling. This handling, in turn, increases the likelihood of damaging the IC devices. Secondly, the size of the infrastructure for applying the epoxy is difficult to scale. This makes it less practicable to adjust manufacturing processes according to production volume requirements. Finally, the relatively slow curing process for epoxy materials reduces the throughput rate of a manufacturing process.
In view of the foregoing, a method for protecting unpackaged IC""s from electromagnetic radiation and which allows a manufacturing mark to be identified upon a surface of the IC""s would be desirable.